Percussion-rotary drill



Nov. 23, 1965 J. c. BOYD 3,219,131

PERGUS S ION-ROTARY DRILL Filed April 27, 1962 INVEN TOR James C.Boyd

@WWM

ATTOR NEY My invention relates to a drilling machineparticularly the drilling or head end of the machinefor drilling a hole into rock, concrete, ground-and-rock strata, or like material, by first cutting a narrow circular cut out of the materialor, if the hole is large, a plurality of spaced concentric narrow circular cutsand then, a short distance back of the cutting bit or bits, applying a succession of blows with one or more narrow percussion bits for breaking up the intervening solid material into broken pieces which are thrust out into the narrow circular or annular cut or cuts.

When the hole to be drilled is so large that a single peripheral narrow circular cut would leave a solid core which is too large to be readily broken apart by providing a single circular cut into which the broken pieces can go, then two or more spaced concentric cuts are needed, depending upon the size of the hole and the nature of the material into which the hole is being drilled.

My invention works on the principle that a little piece can easily be chipped off, near the edge of a solid block of any material which has a very considerable compressive strength or resistance to pounding or compression, but only a small tensile, chipping-resistant or shearingstrength-provided that there is an empty edge space into which th chipped edge pieces can gowhereas, because of its great strength in compression, the material would strongly resist percussive chopping blows which are applied to its center (away from its edge), at a place where there is no space into which the chipped or sheared-off pieces can be laterally pushed or thrust, to get them out of the way.

My invention was primarily designed for boring substantially horizontal holes under a roadway or the like, for receiving utility pipe lines. For such operations, it is quite imperative to keep, to a minimum, the size of the preliminary excavation which is necessary for receiving the drilling-equipment; and this means that the bulk or size of the power-supplying machine which is used at the starting end of the hole must be kept to a minimum. It is also necessary to hold down the weight of such machinery, in order to reduce the time and cost of transporting it to and from the site of operations, the time and cost of mounting ad removing it from the preliminary excavation, and the time and cost of refilling the excavation and resurfacing the refill.

All of these requirements call for a limitation on both the drilling-torque requirements and the thrust requirements, which increase at an exponential rate with any increase in the diameter of the hole to be drilled.

The successful boring of such horizontal holes practically necessitates the use of a plurality of hollow rotating auger-sections, which can be rigidly and detachably fastened together, as the hole-depth (or length) increases, for carrying the cuttings (and chippings) back out of the hole, and for assisting in keeping the hole straight.

With the foregoing ad other principles and considerations in mind, my invention consists of the machines, tools, parts and processes, hereinafter described and claimed, and illustrated in the accompanying drawings, (which are not to scale), wherein:

FIGURE 1 is a schematic longitudinal sectional view of the front end of a percussion-rotary drill, embodying my invention in an exemplary form, the section-plane being shown at II in FIG. 3;

FIG. 2 is a fragmentary schematic longitudinal sec- 3,219,131 Patented Nov. 23, 1965 tional view of the same equipment, the section-plane being shown at IIII in FIG. 3;

FIG. 3 is a schematic end view of the front end of the same equipment, as viewed from the plane III-III in FIG. 2, and

FIG. 4 is a schematic longitudinal sectional view of the front end of the hole as it is being drilled by the equipment of FIGS. 1, 2 and 3, showing, in dotted lines, the positions of the three percussion bits as they are chipping at the solid material between the spaced concentric narrow circular cuts which have been made by the cutting bits (not shown in this view).

The tool which is shown in FIGS. 1 to 3 comprises a plurality of elongated tubular or hollow auger sections or flights 5, which can be rigidly and detachably fastened together, as by tubular air-tight chucks, couplings, or connecting means 6. The exemplary connecting chuck 6, between the two auger flights 5 which are shown in FIG. 1, has a threaded connection 7 at one end, and a telescoping connection 8 at the other end, made air-tight by an O-ring seal 9, and held together by an air-sealed bolt 10.

The front end of the illustrated tool carries a hollow elongated percussion-and-rotary drilling end head 12, the rear end or hub 13 of which is threaded, or otherwise detachably and rigidly fastened, to the front end of the foremost or lead auger section 15, so that the end-head 12 and the foremost auger section 15 constitute, in eifect, a rigid unit which serves as a percussive-rotary drill head 16. The end head 12, the auger flights 5, and the coupling chucks 6 have helical flange sections 17, 18, 19 and 20, which together form a continuous auger helix 21 for carrying the cuttings (and chippings) back out of the hole which is being drilled or bored, and also materially assisting in keeping the hole straight.

The front end 22 of the end-head 12 is flat, or cut away on each side, so as to form a flat projection 22 which presents a generally rectangular, diametrically extending appearance as viewed from its front end, as shown in FIG. 3. This flat front end 22 is widened out from the rear hub 13 of the end-head 12, so as to extend out radially beyond the peripheral radius of said hub 13, as shown in FIGS. 1 and 3. This front end 22 carries one or more narrow forwardly extending cutting bits 23, which rotate with the tool. Each of my cutting bits has a forward cutting edge, which pushes forward against the surface which is to be cut, so as to plane or pare otf shavings or cuttingsas distinguished from a drag-bit which has a negative rake, and which is drawn back in a scraping movement-and also as distinguished from an abrasive bit. Either a narrow forwardly extending drag bit, or a narrow forwardly extending abrasive bit, would require a greater thrust and torque, thus requiring a thicker bit, meaning a wider cut, which in turn would mean more thrust and torque, defeating my objective of a tool which could be driven by a portable low-power, low-weight power plant. My forwardly extending narrow cutting bit 23 is used for making a narrow peripheral circular cut 24; or, in larger drills, a separate forwardly extending narrow cutting bit 23 is used for making each of a plurality of spaced concentric narrow circular cuts 24 (FIG. 4), out of the diverse strata or other material 25 through which the hole 26 is being bored. In the illustrated embodiment of my invention, I use two diametrically opposite cutting -bits 23 for making the peripheral circular cut 24, as shown in FIGS. 1 and 3.

The end-head 12, and the foremost auger flight 15, which together constitute a percussive-rotary drill-head 16, have a plurality of longitudinal guide holes 27, 28, 29, 30, 31 therein, which house the various parts of a self-valving pneumatic percussion tool 34, which is nonrotatably mounted for reciprocating movement within said guide holes. This percussion tool 34 may comprise any well-known valve or valving member 35, a piston 36 which reciprocates within the cylinder or hole 31, an anvil 37, and a percussion head 38 which has a flat front end 39, which passes through a rectangular hole 27 which extends at right angles across the fiat front end 22 of the end head 12, thus providing a mounting means for preventing a rotating movement of the percussion head 38 with respect to the foremost auger flight 15, while guiding said percussion head 38 during its reciprocating move ment. As shown in FIGS. 2 and 3, the flat front end 39 of the percussion head 38 is flattened at its sides, so as to present a generally rectangular, diametrically extending appearance as viewed from the front (in FIG. 3); and it extends out to a radius beyond the guide holes 28, 29 and 30 (FIG. 1) in the front end 22 of the foremost auger section 15.

Thus, both the cutting bits 23 and the percussion bits 43 include a bit or bits which are disposed at a radial distance away from the center-of-rotation line of the rotary drill head 16; while the flat percussion bit head 39 projects forwardly in an axial plane at an angle to the plane of the cutting bit head 22. This construction permits the percussion bit head 39 to perform its chippingaction without interference with the cutting bit head 22, while at the same time it provides spaces whereby the cuttings and chippings can get back out of the hole 26 (FIG. 4) which is being drilled.

The rear of the flat front end 39 of the percussion head 38 is connected to a round stem 40 which slides through the guiding hole 28 in the front part of the hub 13, and which then extends into the larger hole 29, where it merges into a non-round stem 41 which slides through the non-round hole 30 but cannot rotate therein. rounding the rear end of the round stem 40, within the hole 29, a compression spring 42 is mounted, for retracting the percussion head 38 after each blow of the anvil 37, in a manner which is well-known in percussion tools.

In accordance with my invention the flat front end 39 of the percussion tool 34 terminates in one or more narrow, forwardly facing percussion bits 43, which are disposed so as to be operative on the intervening solid material 44 (FIG. 4), between the circular cuts 24, at a short distance back of the cutting bit or bits 23 (FIG. 2), for breaking up said intervening solid material into broken pieces which are thrust out (laterally) into the narrow circular cut or cuts 24 during each rotation of the drill head 16.

At the rearward limit of the reciprocating movement of the percussion tool 34, as shown in FIG. 1 and in full lines in FIG. 2., the fronts of the percussion bits 43 are then back of the fronts of the cutting bits 23, so that the chipping-action of the percussion bits 43 may take place after the circularly moving cutting bits 23 have started cutting their narrow circular cuts 24 (FIG. 4) in the material 25 which is being drilled or bored.

The detachably connected auger flights have longitudinal passages 45 whereby compressed air may be supplied to the pneumatic percussion tool 34, as diagrammatically indicated by the arrow 46, accompanied by the legend AIR, in FIG. 1.

The operation of my illustrated tool, when used for boring a substantially horizontal underground hole, involves the use of certain equipment or machinery at the starting end of the hole, as indicated, in FIG. 1, by: (1), an arcuate arrow 47 which schematically indicates a motive-means for controllably applying a rotating torque to the auger flights 5; (2), two thrust arrows 48 which schematically indicate a (usually reversible) motive means for controllably applying a longitudinal thrust to the back end of the auger flights 5 for pressing the cutting bit or bits 23 against the material to be cut, and resisting the backward reaction of the chopping strokes of the percussion tool 34, thus advancing (and usually also, when Surreversed, withdrawing) the drill; and (3), the air arrow 46 which schematically indicates a source of compressed air for controllably supplying the compressed air for my pneumatic percussion tool 34. This power-supplying equipment or machinery may be of any conventional type, needing no detailed illustration, so that my schematic suggestion thereof, by arrows, should suffice for an understanding of my improved drilling tool or assembly. This power-supplying machinery must be set up in a preliminary excavation (not indicated) at the starting end of the hole 26 (FIG. 4), which is to be drilled.

This power-supplying equipment has heretofore weighed several tons, for drilling a horizontal 8-inch-diarneter hole (for example), through solid rock, with a rotating drill having a sufficient number of cutting bits to cover substantially all of the cross-sectional area of the hole which is being drilled. Such heavy power equipment required long hours for its placement, and necessitated the blocking of streets where it was used.

On the other hand, previous horizontally operating rock drills which have used only percussion bits (without using narrow circular cuts for providing a lateral space into which each percussion bit can thrust its chippings), have not been competitively practicable beyond the very smallest diameters and the very shortest lengths of the hole to be drilled, because of the extremely rapid rate at which their thrust-requirements increased with increases in the hole diameter, and because of the difiiculty in maintaining reasonably straight holes, and also because of sticking when encountering shale or softer materials.

The power supplying equipment 46, 47, 48, for my present drill (again using the illustration of an 8-inch horizontal hole, to be drilled in solid rock), generally requires only a light, portable equipment, weighing something like 200 or 250 pounds, which can be handled by two men. This is because my cutting bits 23 cut out only a small part of the cross-sectional area of the hole, so that their torque and thrust requirements correspond to the requirements for a much smaller hole diameter with the previous drills which used cutting bits for cutting out the entire cross-sectional area of the hole; while the thrust requirements of my percussion-bits are very much smaller, area for area, than in previous drills. which used only percussion bits without providing my narrow circular advance cuts 24 into which the rock chippings could move. Under usually encountered rock conditions, my present drill can drill a 30-foot, 8-inch horizontal hole through solid rock, in about five hours, which is very much less than the time required by any previous drill.

When starting a hole with my present drill, only the turning torque 47 and the thrust 48 are at first applied, letting the cutting bits complete a few revolutions, so as to make a narrow circular cut or cuts 24, to a depth of about half an inch, more or less, into the face of the hole, before the air 46 is applied to the percussion tool 34. The percussion bits 43 then make something like 7 to 50 chops during each revolution of my tool, thus chipping out the solid material inside of (or between) the narrow circular cut or cuts, at 7 to 50 places around the solid material, during each successive revolution, as the circularly moving cutting bits 23 advance into the hole which is being bored. The rapidity and the impact strength of the chopping (percussion) strokes can be adjusted within wide limits, by adjusting the air flow 46 which is supplied to the auger flights 5, to allow for varying rock conditionsor, when soft soil is encountered, the air 46 can be shut off entirely, because percussion is not then needed in order to bore successfully.

It will thus be seen that I have provided an exceedingly versatile instrument, which is capable of coping with the wide varieties of ground conditions which are likely to be encountered in drilling or boring substantially horizontal holes for running utility pipe lines under a roadway or the like. It can handle soft-soil conditions, where little or no chopping is required. It can drill through solid rock-either natural rock or man-made rock such as cement-which has practically no modulus of elasticity,

so that, when it receives a chopping blow near its edge, a very slight fissure will result in breakage or chipping, provided that there is even an extremely narrow lateral space into which the chipped material may begin to move, without encountering lateral support or compression.

Thus, my annular cut or cuts can, and should, be made extremely narrowwith a narrowness which is limited only by the strength of the available bit material, at the point when bit breakage would begin to cause more harm, than the good which could be obtained through the reduced power-requirements of still narrower cutting bits. My narrow circular cut is provided, not for removing any great quantity of the bored-out material, but only for making the narrowest practicable cut. It is a cut to permit the breakage of a rock material which has only a small tensile, chipping-resistant or shearing strength. With presently available bit materials, a bit width of something like %1 inch is about right, provided that the torque and thrust conditions are kept small, which is what I wanted in the first place.

While I have explained my apparatus and its operation to the best of my present understanding, I do not wish to be limited to such explanations, as many modifications, refinements, omissions, additions, and substitutions of equivalents will undoubtedly be made as experience is gained in the manufacture and use of my equipment, and as new uses or applications of my invention are discovered. And of course, the addition of relatively trivial parts are immaterial to the broadest aspects of my invention. For example, while I have described my percussion tool 34 as comprising a reciprocating piston or hammer member 36, and a separate percussion member 38, with a separate reciprocating anvil 37 disposed in between, the percussionmember 38 could have been connected directly to the front end of the hammer member 36, so as to move therewith, since the essential object is that the percussion tool 34 be reciprocated. However, it is usually advantageous to use a separate hammer member 36, which can have a longer stroke than the percussion member 38, so that it can build up a high impact-velocity without being limited by the shorter stroke for which there is room for the reciprocation of the flat front end 39 of the percussion member 38.

In boring any but the shortest holes, some means should be used for mechanically carrying the bored out material back out of the hole, and many such means are known. In the boring of horizontal holes, which is the contemplated (but perhaps not the only), field of application of my invention, the use of auger flights 5 seems to be the best for this purpose, and I have so described the preferred form of embodiment of my invention, because, among other things, these augerflights assist substantially in keeping the hole straight; although it is conceivably possible that there might be conditions where substantial advantages might be gained by using some features of my invention without these auger-flights 5 or the auger helices 21.

While I have illustrated my invention, therefore, in only a single form of embodiment, I wish it to be understood that I am not altogether limited to these precise details, and I desire that the appended claims shall be accorded the broadest interpretation consistent with their language, when read in the light of the described purposes of my invention.

I claim as my invention:

. 1. A rapid, portable, lightweight, low-thrust, lowpower, hollow rotary drill, adapted for boring a substantially horizontal hole through ground-and-rock strata or similar material, under a roadway or the like, for receiving a utility pipe line; said drill comprising: a plurality of hollow rotating auger sections which can be rigidly and detachably fastened together, as the hole penetration increases, for carrying the cuttings back out of the hole, and for assisting in keeping the hole straight; a hollow percussion-and-rotary-drilling end head which is rigidly fastened to the front end of the foremost auger section so as to constitute therewith a percussive rotary drill head, said end head carrying a cutting bit means for first cutting a narrow circular cut out of the material through which a hole is being drilled, leaving uncut intervening solid material; a self-valving pneumatic percussion tool, mounted within the hollows of said foremost auger section and its end head, and adapted to be powered by compressed air which can be passed through the auger sections, said percussion tool having mounting means whereby it has freedom for longitudinal reciprocating movement, but substantially no rotating movement, with respect to the foremost auger section and its end head; the front part of said percussion tool rigidly carrying a percussion bit means, disposed so as to be operative on the intervening solid material, at a short distance back of the drag bit means, for breaking up said intervening solid material into broken pieces which are thrust out into the narrow circular cut during each rotation of the drill head.

2. A rapid, portable, light-weight, low-thrust, lowpower, hollow rotary drill, adapted for boring a substantially horizontal hole through ground-and-rock strata or similar material, under a roadway or the like, for receiving a utility pipe line; said drill comprising: a plurality of hollow rotating auger sections which can be rigidly and detachably fastened together, as the hole penetration increases, for carrying the cuttings back out of the hole, and for assisting in keeping the hole straight; a hollow percussion-and-rotary-drilling end head which is rigidly fastened to the front end of the foremost auger section so as to constitute therewith a percussive-rotary drill head, said end head carrying a plurality of narrow cutting bits disposed at a plurality of radial distances from the center-of-rotation line of the drill, for first cutting out a plurality of spaced concentric narrow circular cuts out of the material through which a hole is being drilled, leaving uncut intervening solid material; and a self-valving pneumatic percussion toll, mounted within the hollows of said foremost auger section and its end head, and adapted to be powered by compressed air which can be passed through the auger sections, said percussion tool having mounting means whereby it has freedom for longitudinal reciprocating movement, but substantially no rotating movement, with respect to the foremost auger section and its end head; the front part of said percussion tool rigidly carrying a plurality of percussion bits, disposed so as to be operative on the intervening solid material, at a short distance back of the drag bits, for breaking up said intervening solid material into broken pieces which are thrust out into the narrow circular cuts during each rotation of the drill head.

3. A rapid, portable, light-weight, low-thrust, lowpower, hollow rotary drill, adapted for boring a substantially horizontal hole through ground-and-rock strata or similar material, under a roadway or the like, for receiving a utility pipe line; said drill comprising: a plurality of hollow rotating auger sections which can be rigidly and detachably fastened together, as the hole penetration increases, for carrying the cuttings back out of the hole, and for assisting in keeping the hole straight; a hollow percussion-and-rotary-drilling end head which is rigidly fastened to the front end of the foremost auger section so as to constitute therewith a percussive-rotary drill head, said end head carrying a cutting-bit means for cutting a narrow circular cut out of the material through which a hole is being drilled, leaving uncut intervening solid material; and a reciprocating percussion-bit means, mounted within the hollows of said foremost augersection and its end head, and disposed so as to be operative on said uncut intervening solid material in such manner as to chip said uncut intervening solid material into '7 broken pieces which are thrust laterally into the circular cut; said reciprocating bit means comprising a mounting means whereby it has freedom for reciprocating movement, but substantially no rotating movement, with respect to said hollow drill, and further comprising a separately controllable reciprocating power means for causing said reciprocating percussion bit means to deliver a succession of chipping blows to said uncut intervening solid material during each rotation of said drill, the rearward limit of the reciprocating movement of said percussion bit means being such that the front of the percussion bit means is then back of the front of the cutting bit means.

4. A rapid, portable, light-weight, low-thrust, lowpower, 'hollow rotary drill, adapted for boring a substantially horizontal hole through ground-and-rock strata or similar material, under a roadway or the like, for receiving a utility pipe line; said drill comprising: a plurality of hollow rotating auger sections which can be rigidly and detachably fastened together, as the hole penetration increases, for carrying the cuttings back out of the hole, and for assisting in keeping the hole straight; a hollow percussion-and-rotary-drilling end head which is rigidly fastened to the front end of the foremost auger section so as to constitute therewith a percussive-rotary drill head, said end head carrying a separate forwardly extending narrow cutting bit, disposed at each of a plurality of different radial distances from the center-ofrotation line of the drill, for making each of a plurality of concentric narrow circular cuts out of the material through which a hole is being drilled, leaving uncut intervening solid material; and a reciprocating percussion bit means, mounted within the hollows of said foremost auger section and its end head, and disposed so as to be operative on said uncut intervening solid material in such manner as to chip said uncut intervening solid material into broken pieces which are thrust laterally into the circular cuts; said reciprocating bit means comprising a mounting means whereby it has freedom for reciprocating movement, but substantially no rotating movement, with respect to said hollow drill, and further comprising a separately controllable reciprocating power means for causing said reciprocating percussion bit means to deliver a succession of chipping blows to said uncut intervening solid material during each rotation of said drill, the rearward limit of the reciprocating movement of said percussion bit means being such that the front of the percussion bit means is then back of the front of the cutting bit.

5. A rapid, portable, light-weight, low-thrust low-power, hollow rotating drill head, adapted for drilling a substantially horizontal hole through ground-and-rock strata or similar material, under a roadway or the like; said drill head comprising: an elongated hollow body-section portion having a peripheral helix; a hollow end head portion having its rear end rigidly carried by the front end of said hollow body section portion; a narrow forwardly extending cutting bit, rigidly carried by the front end of said end head portion, said cutting bit having a forward cutting edge in such position as to plane or pare oif shavings or cuttings, which result in a narrow peripheral circular cut out of the material through which a hole is being drilled, leaving uncut solid material inside of said narrow circular cut; a reciprocating percussion bit head, having a rear stem having a slidable mounting within the hollows of the end head and body section portions, said slidable mounting providing freedom for longitudinal movement, but substantially no rotational movement, of said percussion bit head with respect to said drill head, the front end of said percussion bit head having forwardly facing percussion bit means, disposed in such manner as to chop close to the periphery of said uncut solid material, but without interference with said drag bit means; the rearward limit of said longitudinal movement being such that the front of the percussion bit head is then back of the front of the cutting bit; and a reciprocating hammer member and it separately controllable power 8 means for said hammer member, both mounted within a. rear part of the hollow body section portion, for causing the reciprocation of said hammer member to deliver a plurality of blows to the rear end of the rear stem of the reciprocating percussion bit head during each rotation of the drill head.

6. A rapid, portable, light-weight, low-thrust, lowpower, hollow rotating drill head, adapted for drilling a substantially horizontal hole through ground-and-rock strata or similar material, under a roadway or the like; said drill head comprising: an elongated hollow body section poition; a hollow end head portion having its rear end rigidly carried by the front end of said hollow body section portion; said hollow end head portion rigidly carrying a plurality of forwardly extending narrow cutting bits, disposed at a plurality of radial distances from the centerof-rotation line of the drill head, for cutting a plurality of concentric narrow circular cuts out of the material which is being drilled, the smallest circular cut leaving a central core of uncut solid material therewithin, and each pair of successively larger circular cuts having an annular body of uncut solid material therebetween; a reciprocating percussion bit head, having a rear stem having a slidable mounting within the hollows of the end head and body section portions, said slidable mounting providing freedom from said center-of-rotat-ion line will make chipping cutsclose to the edges of the successive annular bodies of uncut solid material; the rearward limit of said longitudinal movement being such that the front of the percussion bit head is then back of the front of the cutting bits; and a reciprocating hammer member and a separately controllable power-means for said hammer member, both mounted within a rear part of the hollow body section portion, for causing the reciprocation of said hammer member to deliver a plurality of blows to the rear end of the rear stem of the reciprocating percussion bit head during each rotation of the drill head.

'i. A hollow elongated rotating drill, particularly adapted for drilling a substantially horizontal hole into diverse ground-and-rock strata or similar material; said drill having a peripheral flange which serves as an auger helix for carrying the cuttings back out of the drilled hole; a hollow end head portion having a rear hub portion rigidly connected to the front end of said drill, said hollow end head portion having a flat front end which extends out radially beyond the periphery of its rear hub portion; forwardly extending narrow cutting bit means, rigidly connected to said flat front end of the hollow end head portion, for cutting a narrow circular cut around the periphery of the drilled hole, leaving uncut intervening solid material; and a pneumatic, rapidly reciprocating, self valving percussion tool, mounted within said drill, and adapted to be powered by compressed air which can be passed through the rear part of the hollow in the drill; said percussion tool including a percussion head hav ing -a mounting means whereby said percussion head has freedom for longitudinal movement, but substantially no rotational movement, with respect to said drill; said percussion head having a fiat front end, which extends out: radially beyond the hollow in the drill, and which further is provided with a percussion bit means including a bit which is disposed at a radius beyond said hollow, for chipping away the edges of the uncut intervening solid material immediately within said narrow peripheral circular cut, the rearward limit of the reciprocating movement of said percussion bit means being such that the front of the percussion bit means is then back of the front of the cutting bit means.

8. A hollow elongated rotating drill, particularly adapted for drilling a substantially horizontal hole into diverse ground-and-rock strata or similar material; said drill having a peripheral flange which serves as an auger helix for carrying the cuttings back out of the drilled hole; a hollow end head portion having a rear hub portion rigidly connected to the front end of said drill, said hollow end head portion having a flat front end Which extends out radially beyond the periphery of its rear hub portion; forwardly extending narrow cutting bit means, rigidly connected to said fiat front end of the hollow end head portion, and having a plurality of narrow cutting bits disposed at a plurality of radial distances from the centerof-rotation line of the drill, for cutting a plurality of concentric narrow circular cuts out of the material which is being drilled, the smallest circular cut leaving a central core of uncut solid material therewithin, and each pair of successively larger circular cuts leaving an annular body of uncut solid material therebetween; and a pneumatic, rapidly reciprocating, self valving precussion tool, mounted within said drill, and adapted to be powered by compressed air which can be passed through the rear part of the hollow in the drill; said percussion tool including a percussion head having a mounting means whereby said percussion head has freedom for longitudinal movement, but substantially no rotational movement, with respect to said dn'll; said percussion head having a flat front end, which extends out radially beyond the hollow in the drill, and which further is provided with a percussion bit means including a plurality of chopping bits, disposed at a plurality of radially separated points with respect to the center-of-rotation line of the drill, in such positions that a chopping bit which is relatively close to said centerof-rotation line will make chipping cuts close to the periphery of said central core of uncut solid material, whereas other chopping bits which are successively further out from said center-of-rotation line will make chipping cuts close to the edges of the successive annular bodies of uncut solid material, the rearward limit of the reciprocating movement of said percussion bit means being such that the front of the percussion bit means is then back of the front of the cutting bit.

9. A relatively low-thrust, low-torque, rotating drill, particularly adapted for drilling a long, straight, substantially horizontal hole into diverse ground-and-rock strata or similar material; said drill comprising: a plurality of hollow elongated rotating auger sections having connecting means whereby they can be rigidly, detachably, and air-tightly fastened together, as the depth of the drilled hole increases, for carrying the cuttings back out of the drilled hole, and for assisting in keeping the drilled hole straight; the foremost auger section rigidly including a hollow end head portion having a flat front end which extends out radially beyond the periphery of its rear end; a forwardly extending narrow cutting bit, rigidl connected to said flat front end of the hollow end head portion, for cutting a narrow circular cut around the periphery of the drilled hole, leaving uncut intervening solid material; and a pneumatic, rapidly reciprocating, self-valving percussion tool, mounted within said foremost auger section, and adapted to be powered by compressed air which can be passed through the successive auger sections to said foremost auger section; said percussion tool including a percussion head having a mounting means, within said foremost auger section, whereby said percussion head has freedom for longitudinal movement, but substantially no rotational movement, with respect to said foremost augersection; said percussion head having a flat front end, which extends out radially beyond the hollow in said foremost auger section, and which further is provided with a percussion bit means including a bit which is disposed at a radius 1% beyond said hollow, for chipping away the edges of the uncut intervening solid material immediately within said narrow peripheral circular cut, the rearward limit of the reciprocating movement of said percussion bit means being such that the front of the percussion bit means is then back of the front of the cutting bit.

10. A relatively low-thrust, low-torque rotating drill, particularly adapted for drilling a long, straight, substantially horizontal hole into diverse ground-and-rock strata or similar material; said drill comprising: a plurality of hollow, elongated rotating auger-sections having connecting means whereby they can be rigidly, detachably, and air-tightly fastened together, as the depth of the drilled hole increases, for carrying the cuttings back out of the drilled hole, and for assisting in keeping the drilled hole straight; the foremost auger section rigidly including a hollow end head portion having a flat front end which extends out radially beyond the periphery of its rear end; a forwardly extending narrow cutting bit means, rigidly connected to said flat front end of the hollow end head portion, and having a plurality of narrow cutting bits disposed at a plurality of radial distances from the center-ofrotation line of the drill, for cutting a plurality of concentric narrow circular cuts out of the material which is being drilled, the smallest circular cut leaving a central core of uncut solid material therewithin, and each pair of successively larger circular cuts leaving an annular body of uncut solid material therebetween; and a pneumatic, rapidly reciprocating, self-valving, percussion tool, mounted within said foremost auger section, and adapted to be powered by compressed air which can be passed through the successive auger sections to said foremost auger section; said percussion tool including a percussion head having a mounting means, within said foremost auger section, whereby said percussion head has freedom for longitudinal movement, but substantially no rotational movement, with respect to said foremost auger section; said percussion head having a flat front end, which extends out radially beyond the hollow in said foremost auger section, and which further is provided with a percussion bit means, including a plurality of chopping bits, disposed at .a plurality of radially separated points with respect to the center-of-rotation line of the drill, in such positions that a chopping bit which is relatively close to said center-of-rotation line will make chipping cuts close to the periphery of said central core of uncut solid material, whereas other chopping bits which are successively further out from said centerof-rotation line will make chipping cuts close to the edges of the successive annular bodies of uncut solid material, the rearward limit of the reciprocating movement of said percussion bit means being such that the front of the percussion bit means is then back of the front of the cutting bit means.

References Cited by the Examiner UNITED STATES PATENTS 1,075,027 10/ 1913 Ebbley 299-62 2,054,255 9/1936 Howard 175415 X 2,625,376 1/ 1953 Smith 17562 X 2,665,117 1/1954 Ivey l62 X 2,818,233 12/1957 Williams 330 2,868,511 1/1959 Barrett 17592 2,873,093 2/1959 Hildebrandt et al. 17592 2,901,231 8/1959 Hagenbook 29986 2,969,844 1/ 1961 Hamrick 17562 X 3,008,698 11/1961 Risse et al 175333 3,074,703 1/1963 Adams 175-39 8 X 3,078,933 2/1963 Orner 175-62 X 3,092,190 6/1963 Gruere 17562 X 3,130,799 4/1964 Williams 17592 CHARLES E. OCONNELL, Primary Examiner. 

5. A RAPID, PORTABLE, LIGHT-WEIGHT, LOW-THRUST LOW-POWER, HOLLOW ROTATING DRILL HEAD, ADAPTED FOR DRILLING A SUBSTANTIALLY HORIZONTAL HOLE THROUGH GROUND-AND-ROCK STRATA OR SIMILAR MATERIAL, UNDER A ROADWAY OR THE LIKE; SAID DRILL HEAD COMPRISING: AN ELONGATED HOLLOW BODY-SECTION PORTION HAVING A PERIPHERAL HELIX; A HOLLOW END HEAD PORTION HAVING ITS REAR END RIGIDLY CARRIED BY THE FRONT END OF SAID HOLLOW BODY SECTION PORTION; A NARROW FORWARDLY EXTENDING CUTTING BIT, RIGIDLY CARRIED BY THE FRONT END OF SAID END HEAD PORTION, SAID CUTTING BIT HAVING A FORWARD CUTTING EDGE IN SUCH POSITION AS TO PLANE OR PARE OFF SHAVINGS OR CUTTINGS, WHICH RESULT IN A NARROW PERIPHERAL CIRCULAR CUT OUT OF THE MATERIAL THROUGH WHICH A HOLE IS BEING DRILLED, LEAVING UNCUT SOLID MATERIAL INSIDE OF SAID NARROW CIRCULAR CUT; A RECIPROCATING PERCUSSION BIT HEAD, HAVING A REAR STEM HAVING A SLIDABLE MOUNTING WITHIN THE HOLLOWS OF THE END HEAD AND BODY SECTION PORTIONS, SAID SLIDABLE MOUNTING PROVIDING FREEDOM FOR LONGITUDINAL MOVEMENT, BUT SUBSTANTIALLY NO ROTATIONAL MOVEMENT, OF SAID PRECUSSION BIT HEAD WITH RESPECT TO SAID DRILL HEAD, THE FRONT END OF SAID PRECUSSION BIT HEAD HAVING FORWARDLY FACING PRECUSSION BIT MEANS, DISPOSED IN SUCH MANNER AS TO CHOP CLOSE TO THE PERIPHERY OF SAID UNCUT SOLID MATERIAL, BUT WITHOUT INTEREFERENCE WITH SAID DRAG BIT MEANS; THE REARWARD LIMIT OF SAID LONGITUDINAL MOVEMENT BEING SUCH THAT THE FRONT OF THE PERCUSSION BIT HEAD IS THEN BACK OF THE FRONT OF THE CUTTING BIT; AND A RECIPROCATING HAMMER MEMBER AND A SEPARATELY CONTROLLABLE POWER MEANS FOR SAID HAMMER MEMBER, BOTH MOUNTED WITHIN A REAR PART OF THE HOLLOW BODY SECTION PORTION, FOR CAUSING THE RECIPROCATION OF SAID HAMMER MEMBER TO DELIVER A PLURALITY OF BLOWS TO THE REAR END OF THE REAR STEM OF THE RECIPROCATING PRECUSSION BIT HEAD DURING EACH ROTATION OF THE DRILL HEAD. 